A linear drive arrangement of the above-mentioned type is for example known from German Pat. No. 20 55 721. The planet guide rollers rest under pressure on the surface of the wire and rotate in a plane which is at a right angle with respect to the axis of rotation. Since the planet guide rollers define an angle with the wire axis, the wire is moved forwardly by the rotating planet guide rollers. The guide roller holders of the known planet guide roller feed arrangement are constructed as pistons and are supported on a conical cylinder surface of an adjusting nut which can be rotated about the welding wire. The adjusting nut can be moved axially in direction of the axis of rotation. With this an even feed of the planet guide rollers through one single adjusting nut is achieved.
From German GM No. 76 20 049 it is furthermore known to arrange the planet guide rollers on a two-arm lever, the other end of which slides on a tensioning cone ring, which is also rotatable about the axis of the wire and can be moved in axial direction with respect to the wire axis. The tensioning cone ring is biassed by a spring in axial direction, through which the centrifugal forces are to be compensated and a reproducible contact pressure is to be obtained for each wire diameter.
These known planet guide roller feed arrangements are on the one hand relatively complicated in structure and thus expensive to manufacture and require on the other hand during each new insertion of the welding wire considerable adjusting operations. Thus, for example, in the case of a planet guide roller feed arrangement according to German Gebrauchsmuster No. 76 20 049, a nut must be rotated every time, which causes the planet guide rollers to be moved away from one another, so that the wire can be moved in place. Then the new adjustment of the contact pressure occurs. The same is true for a planet guide roller feed arrangement according to German Pat. No. 20 55 721.
The basic purpose of the invention is to construct a planet guide roller feed arrangement of the above-mentioned type so that same is extremely simple in structure and thus inexpensive in the manufacture and requires only a small input for the adjustment of the planet wheels.
This purpose is inventively attained by the bearing part consisting of a sleeve which is slotted in axial direction over the important part of its length, by arranging on each part of the slotted end of the bearing part a planet guide roller and by the feed of the bearing part and thus of the planet guide rollers occurring through an axial movement of the bearing part relative to a gripping member which encloses same. According to a further solution of the invention, the gripping member consists of a guide ring, wherein the feed of the planet guide rollers occurs by reducing the diameter of the guide ring.
An inventive planet guide roller feed arrangement can be manufactured inexpensively due to its simple structure so that it is economically acceptable to use a planet guide roller feed arrangement only for a narrowly limited range of diameters. The exchange of the entire planet guide roller feed arrangement during a changing of the welding-wire thickness is then more advantageous with respect to expense than the time-consuming adjustment of the planet guide roller feed arrangement to the new welding-wire thickness. An inventive planet guide roller feed arrangement is adjusted by the manufacturer to a predefined range of welding-wire diameters. The user no longer has to make an adjustment.
In order to design the basic adjustment of an inventive planet guide roller feed arrangement as simply as possible, a gripping member has advantageously a precisely defined internal bore and the bearing piece, more exactly the part of the bearing piece which forms a clamping sleeve, has a precisely defined outside diameter. To adjust the planet guide roller feed arrangement, it is only necessary to suitably choose the inside diameter of the gripping member and the outside diameter of the bearing piece. In case that a guide ring is used for the adjustment of the planet guide rollers, it is possible to make the adjustment easier by choosing the guide ring in such a manner that at a maximum possible feed the desired contact pressure of the planet guide rollers on the welding wire is just achieved.